1. Field of the Invention
This invention is concerned with a new and improved drilling machine and cutting bits or cutters therefor and more particularly to drilling machines which are especially adapted to the drilling of metal-clad doors to provide a hole for the knob and lock mechanism and another hole for the latch mechanism. The novel drilling machine is for the processing of metal-clad doors which have come into extensive use for protection of homes and offices and the like against unlawful entry. The drilling of the knob and lock mechanism opening on a metal-clad door requires a different drilling or cutting mechanism than has been customarily used. This invention therefore is concerned with an improved drilling apparatus constructed especially for handling the drilling of metal-clad doors to provide the bore for receiving the lock mechanism and handle of the door knob and another opening for the latch portion of the knob and lock assembly. In drilling mechanisms for drilling holes in metal-clad doors one important and necessary feature is an arrangement for ejection of the core which is cut out by the hole cutter. Another feature which is important in a drilling machine of this type is the provision of a hole cutter or hole saw which will cut through the metal-clad portion and the innermost diameter of the hole cut so that the core of metal which is cut will not interfere with the cutting of the wooden door inside.
2. Description of the Prior Art
A variety of patented hole cutting saws or machines are illustrated in the prior art. Typical hole cutting saws or machines are illustrated in U.S. Pat. Nos. 508,795; 1,348,190; 2,606,615; 2,978,002; 3,130,763; and 3,574,946. These patents disclose or teach a variety of forms of hole cutting apparatus and some include features for discharge of the core which is cut in forming a hole in the material being processed. None of these prior art devices, however, disclose a hole cutter in which the core drops after it is cut and is ejected automatically through the support mechanism for the hole cutter or hole saw. Also, none of the prior art discloses a hole cutter in which the cutting teeth are designed to cut through a metal-clad wooden object, such as a metal-clad door, in such a manner that the innermost portion of the hole is cut through the metal cladding before the cutter begins to cut into the wooden core inside. This feature is essential in the cutting of metal-clad objects to prevent the disc of metal which is cut out first from interferring with the operation of the cutter in cutting out a core from the wooden core within the metal cladding.